I have 3D application which am porting from TaoFramework to OpenTK and glControl , the problem is that whenever I use glUseProgram , glBindBuffer (apparently openGL 1.5 and higher functions) I get an exception like this "Unable to find an entry point named 'glGenBuffers' in DLL 'opengl32.dll'". , though that didn't happen when tried to create a separate test application that uses glUseProgram. and btw am sure that I have the latest drivers and graphics card that supports openGL 3.

Are you using OpenTK.Compatibility.dll to access Tao.OpenGl or are you using OpenTK.dll to access OpenTK.Graphics.OpenGL?

When using OpenTK.Graphics, this exception should only occur if the function really isn't supported (e.g. you are getting a non-accelerated context).

When using Tao.OpenGl (both through Tao.OpenGl.dll or OpenTK.Compatibility.dll), this may happen when accessing any OpenGL function before creating an OpenGL context. In that case, you need to step through the code, find the culprit and remove it (the issue typically lies in Resize event handlers, so check those first).

Actually I use OpenTK.dll to access OpenTK.Graphics.OpenGL, I use the comparability to access some of the glu functionality.
The glGetString Returns a non-accelerated Microsoft context , it should be nvidia instead , and there was no problem with the other test applications. Any Ideas ?

Try running your application with the debug version of OpenTK.dll (you can find it in Binaries/OpenTK/Debug). This dll will print debug info to the output window of Visual Studio - attach this info here so I can take a look. I haven't really seen this kind of issue before.

It would also help if you posted what video card and drivers you are using. Do other OpenGL applications work correctly? What about the samples in Examples.exe?

Finally I was able to find the problem. my application used to "fade in" at start, I only did that as an effect by playing with Opacity property in the Form , it worked when I used TaoFramework , while it resulted in not initializing glControl correctly -or maybe it initialized correctly but after that when the opacity changes the openGL context is replaced by Generic Microsoft GDI context, thats what I can understand-.
Any way is this a bug in the glControl ? because it didn't happen with SimpleOpenGL control from TaoFramework ??

here is a sample that reproduce the bug, it only happens when the opacity of the form is changed at start up of the application.
in the sample the form opacity is set to 50% , that will cause the context to be microsoft generic.
while changing that to 100% will result in successful context creation .
btw I think this is a minor issue.